In recent years, a sensor net is widely used. Within the sensor net, many wireless communication terminals are connected by short-distance wireless communication links. However, there are various problems with the sensor net (refer to James Newsome and Elaine Shi and Dawn Song and Adrian Perrig “The sybil attack in sensor networks: analysis & defense”, IPSN'04: Proceedings of the third international symposium on Information processing in sensor networks, Berkeley, Calif., USA, 2004, ISBN 1-58113-846-6, p. 259-268, ACM Press). In a certain situation, corrupt data may flow into the sensor net due to the use of a forged wireless communication terminal. In another situation, communication resources may be occupied to cause a denial of service.
To avoid such illegal accesses, it is necessary that the wireless base station perform a stringent authentication process on wireless communication terminals and reject any illegal terminal when it issues a request for connection to the network.
Under these circumstances, for instance, JP 2004-282295 A discloses a wireless communication terminal authentication system, which is based on a one-time password authentication method. When the one-time password authentication method is used, the password is changed whenever authentication is performed.
Further, for instance, Poupard and J. Stern “Security analysis of a practical ‘on the fly’ authentication and signature generation, Advances in cryptology—Eurocrypt' 98, Lecture Notes in Computer Science 1403, Springer-Verlag” 1998, p. 422-436 proposes a technology for using digital coupons, which cannot be used repeatedly, instead, for instance, of transportation tickets.